Bootstrapped Switch Circuit Using an Auxiliary Loop for Faster Sampling
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Solution Overview
Problem
Bootstrapped switch circuits face slow switching speeds due to parasitic capacitance, which slows down both the activation and deactivation of the loop circuit, thereby reducing the sampling speed of the input voltage.
Innovation Solution
A bootstrapped switch circuit is enhanced with a main loop circuit and an auxiliary loop circuit, where the auxiliary loop circuit quickly generates a replica bootstrap voltage to drive the second loop transistor, reducing turn-on time and including a third loop transistor to assist in turn-off, thus increasing switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate of the bootstrapped switch transistor has high parasitic capacitance to ensure proper switching operation, then the switching on (activation) of the loop circuit is slowed down, and the deactivation is also slowed down, reducing the sampling speed
Solution Approach 1:
The auxiliary loop circuit generates the replica bootstrap voltage in advance before the main bootstrapped switch needs to switch on. This preliminary voltage generation is stored in the capacitor, ready to immediately charge the gate when needed, eliminating the delay caused by charging the parasitic capacitance during the switching moment.
Solution Approach 2:
The replica bootstrap voltage generated by the auxiliary loop circuit acts as an intermediary that prepares the charging voltage in advance. Instead of directly charging the bootstrapped switch gate during switching (which would be slow due to parasitic capacitance), the system uses this pre-generated replica voltage to rapidly charge the gate when switching is required.
2Device complexity
If a traditional bootstrapped switch circuit is used, then the circuit structure is simple, but the sampling speed is reduced due to slow turn-on and turn-off of the loop circuit
Solution Approach 1:
The bootstrapped switch circuit is segmented into two independent functional loops: a main loop that contains the bootstrapped switch transistor for voltage sampling, and an auxiliary loop that generates the replica bootstrap voltage. This segmentation allows the auxiliary loop to prepare voltage in advance without interfering with the main loop's sampling operation, thereby increasing sampling speed while maintaining manageable circuit complexity.
Solution Approach 2:
The auxiliary loop circuit creates a replica (copy) of the bootstrap voltage that is functionally identical to what the main loop would generate, but produces it in advance and stores it in a capacitor. This copied voltage is then used to rapidly charge the gate of the bootstrapped switch transistor, eliminating the time penalty associated with real-time voltage generation and overcoming the speed limitation of the traditional single-loop design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly enhances the turn-on speed of the bootstrapped switch transistor by rapidly boosting the replica bootstrap voltage, and improves turn-off speed by isolating the gate voltage, resulting in faster sampling of the input voltage.
Implementation Method 1
a positive terminal of a bootstrap capacitor is charged to a power supply voltage with respect to a negative terminal of the bootstrap capacitor
Data Source
AI summary
A bootstrapped switch circuit includes an auxiliary loop circuit for assisting the boosting of a bootstrap voltage in a main loop circuit having a bootstrapped switch transistor. The boosted bootstrap voltage switches on the bootstrapped switch transistor so that an input voltage signal may conduct through the bootstrapped switch transistor to charge a sampling node.